As shown in FIG. 1 of accompanying drawings, a conventional iron golf club of the prior art comprises mainly a head 1 and a shaft 10. The head 1 is provided with a striking blade 11 of an appropriate inclination. The head 1 is provided further at one end thereof with a hosel 12 having a bore 13 dimensioned to receive therein a lower end of the shaft 10. Such a prior art golf club has inherent shortcomings, which are expounded upon explicitly hereinafter.
The bore 13 of the hosel 12 of the prior art golf club head 1 has a closed bottom end. In order to facilitate fastening of the head 1 to the shaft 10, the hosel 12 is increased in length so that the depth of the bore 13 also can be increased. However, such an expedient of deepening the hosel 12 can bring about an adverse effect that the lengthened hosel 12 will reduce the ball-striking mass of the blade, and that the weight of the striking blade 11 therefore is so lessened as to undermine the ball-striking force of the striking blade 11.
As shown in FIG. 1, the bore 13 of the hosel 12 has a bottom end, which is designated as B and which must be higher than the center point A of the striking blade 11. As a result, upon hitting a golf ball, the head 1 is bound to generate the shock of a relatively greater magnitude while the bottom end of the shaft 10 is under a greater torsional stress. The ball-striking effect and the service life span of the golf club of the prior art therefore seriously undermined.
With a view to overcoming the shortcomings described above, a series of improved golf club heads are disclosed in U.S. Pat. Nos. 4,995,609; 5,067,711; 5,222,734; and 5,165,688. As illustrated in FIGS. 2 and 3, the above-mentioned disclosures comprise in common a head 1 having a hosel 12 which is provided with a bore 13 extending to reach the bottom portion of the head 1. In addition, the hosel 12 is shortened in length so as to increase the ball-striking mass of the striking blade 11 for better ball-striking effect. Furthermore, the bottom end B of the shaft 10 is relocated at a level lower than that of the center point A of the striking blade 11 for minimizing the shock generated by the head 1 upon hitting a golf ball and the torsional stress exerting on the shaft 10 at the time when the head 1 hits a golf ball.
The improved golf club heads disclosed in the above mentioned U.S. patents have inherent shortcomings, which are expounded explicitly hereinafter.
The bore 13 of the hosel 12 is extended through the bottom of the head 1. In order to prevent such "bore-through" design from undermining the structural strength of the striking blade 11 and to prevent the bottom end of the bore 13 and the bottom portion of the head 1 from forming an acute angle, the striking blade 11 of the head 1 is extended outwards for a distance. As shown in FIG. 6, the distance E between the center of the bore 13 and the rear line of the striking blade 11 is largely greater than the distance C of the prior art, and this will result in an uncomfortable feeling to the user when addressing, thereby requiring the user thereof to do more swinging practice so as to get accustomed to such a new golf club head as disclosed in the aforementioned U.S. patents.
As the bore 13 is extended through the bottom portion of the head 1, the shaft 10 cannot be located easily. In addition, the bottom end of the shaft 10 extends beyond the bottom portion of the head 1, as shown by the dotted line of FIG. 2. The extended portion of the bottom end of the shaft 10 must be removed by grinding, thereby resulting in waste of material and an increase in production cost. The extra portion of the bottom end of the shaft 10 may be removed before the shaft 10 is fastened with the head 1. However, such a practice is not feasible in view of the fact that the removal of the extra portion of the bottom end of the shaft 10 must be done with precision, and that the shaft 10 cannot easily be located in the bore 13.
When the golf club is used to strike a golf ball, the entire structure of the club is subjected to a tremendously large impact force. The shaft 10, disposed in the bore 13, after a period of use of the shaft 10, the adhering structure of the shaft 10 is bound to loosen to cause the shaft 10 to penetrate to destroy the matter. In addition, the material and the structural strength of the shaft 10 are different from those of the head 1. When the bottom of the shaft 10 is completely exposed through the bore 13 whose bottom end is not appropriately protected, the bottom of the shaft 10 is susceptible to damage caused by the collision and the abrasion between the club and the ground surface or other object when the shaft 10 is in the process of use, thereby affecting the effect of the use of the shaft 10.